Oil Breather Cap Styles

[Bob Riding]

As I am reassembling my 230, I noticed that I have 3 different styles of oil breather caps in my parts stash- from a '56, a '51 and unknown motor. I'm intrigued with the silver one with what looks like a vacuum line adapter. It doesn't look homemade. Would that possibly be for an early PVC setup as posted by @MarcDeSoto?

[MarcDeSoto]

Could it be from a 60s slant six off of a Dodge Dart?

 

[Bob Riding]

Possible- what was the vacuum line attached to?

[Sniper]

It's not a vacuum line, it goes to the clean side of the air cleaner housing.  It provides clean air to the crankcase to replace the stuff the PCV vale removes.

[Bob Riding]

1 hour ago, Sniper said:

It's not a vacuum line, it goes to the clean side of the air cleaner housing.  It provides clean air to the crankcase to replace the stuff the PCV vale removes.

Interesting. So if I install a PCV setup, I should use this cap and install the line to the air cleaner. What is the downside of a PCV system without it?

[Sniper]

You need to provide some sort of filtered air to the crankcase if you want to run a PVC setup.  The other two breathers in the picture have a built in filter.  How well they work I don't know.

[capt den]

Bob, my 1954 265 uses the one in the middle. if you want original decals bernbaum or roberts has them. i have also seen them on ebay.   dennis

[YukonJack]

Bottom one looks like a Ford with a fitting for a hose to the air cleaner. Top on looks like what was on my 47 Plymouth,

 

[harmony]

In an effort to not highjack this post.  Lets say you decided to go with the top one which as Yukon Jack suggested it looks like a late 40's cap.  Can someone suggest the best way to clean them?

I want to clean the one on my '46 251, and I'd also like to clean the oil bath air cleaner.  I think it might get a bit expensive to soak them in brake cleaner, over and over again.  Especially the oil bath air cleaner.  What about using denatured Alcohol to clean them?

[JerseyHarold]

I once read that you can pour a flammable liquid (NOT gasoline!) into the oil cap, set it on fire, and that would clean it out.  Proceed at your own risk!

[Sniper]

The FSM says

 

"Oil Filler Cap; Outlet Pipe Air Cleaner - Wash in kerosene, dry and saturate with SAE 50 engine oil"

[greg g]

Surprised  no one put up the gym sock version.  White sock with three alternating colored stripes mechanics wire tie down.  Or was that a Ford upgrade option?

 

I hear those foam beer can coozies work too.  

 

My 46 has the top one, late 30s had a one looked like a louvered Homburg  hat, middle one looks mid 50s.  Wasn't the hose connection sucking crank vapors into the intake?

 

Edited March 5, 2023 by greg g

[Loren]

The one on the far right with the hose connection should be plumbed to the air cleaner. Usually to the side of a dry filter housing. Most auto parts stores have a plastic part that goes in the inside with a piece of foam ( or other filter material ) that has a clip on the outside. The idea being it is not on the vacuum side of the paper filter. I made the mistake of piping a breather to my transmission ONCE, on the vacuum side and almost sucked all the lube out. The tip off was the cloud of oil smoke following the car at WOT.

If you use a filter type filler cap, then the system is not considered "Closed".

There has to be a vent ( into the crankcase ) as the engine at idle can build up a whole lot of vacuum and suck in the engine oil.

With the filter I described above you have a "Closed" system as the engine vacuum sucks in the crankcase vapors ( when there is vacuum, like idle ) and the carburetor sucks them in under WOT conditions. Either way the blowby gets burnt.

The point of the "Road Draft Tube" was to create a low pressure in the crankcase by the air passing under the car. The oil filler cap served to allow air to enter the crankcase to prevent oil being sucked out the road draft tube. Seems like such a no brainer that they should have been using PCV all along!

But again I believe it was the General that discouraged automotive innovation in the post war era.

[Bob Riding]

17 hours ago, Loren said:

The one on the far right with the hose connection should be plumbed to the air cleaner. Usually to the side of a dry filter housing. Most auto parts stores have a plastic part that goes in the inside with a piece of foam ( or other filter material ) that has a clip on the outside. The idea being it is not on the vacuum side of the paper filter. I made the mistake of piping a breather to my transmission ONCE, on the vacuum side and almost sucked all the lube out. The tip off was the cloud of oil smoke following the car at WOT.

If you use a filter type filler cap, then the system is not considered "Closed".

There has to be a vent ( into the crankcase ) as the engine at idle can build up a whole lot of vacuum and suck in the engine oil.

With the filter I described above you have a "Closed" system as the engine vacuum sucks in the crankcase vapors ( when there is vacuum, like idle ) and the carburetor sucks them in under WOT conditions. Either way the blowby gets burnt.

The point of the "Road Draft Tube" was to create a low pressure in the crankcase by the air passing under the car. The oil filler cap served to allow air to enter the crankcase to prevent oil being sucked out the road draft tube. Seems like such a no brainer that they should have been using PCV all along!

But again I believe it was the General that discouraged automotive innovation in the post war era.

Thanks Loren, great explanation on the physics, but I'm not clear about it being plumbed to the side of a dry filter housing. Does that mean you need to convert the oil bath to a paper filter element? Also would you have a picture of the "plastic part"?

[Loren]

I am working on a Power-Pack manifold and Bendix-Stromberg WW carburetor as we speak. I found an Air Cleaner on eBay for a 1957 Plymouth V8 which uses a dry paper filter and fits the Stromberg. So because you asked I will go to NAPA and get that piece. ( photo to follow )

When I got my 52 Suburban it had two die cast hose fittings screwed to the top of the oil bath filter. It was a California car and I am guessing had been retro fitted with their version of PCV. Of course there was never any provision made for spare parts so if one thing is missing from a retro-fit kit it became non-functional. On an Oil bath the air passage creates a 180 degree corner the air has to go around. Centrifugal force causes dirt to land on the surface of the oil and become trapped. Most of the body of an oil bath filter is made up of a silencing chamber. The more posh Special Deluxe cars got the big filter and the cheapy Deluxe got the little filter. Since I've owned both I can tell you it is real noticeable.

Carl Kiekhaefer in his NASCAR racing program carefully dyno tested his Chrysler engines looking for advantages, within the rules of course.

The first phone call to Chrysler had to of been about oil bath air filters. At the top end they really robbed the engine of air flow and he would have noticed that right away.

If you are going to use an oil bath I'd look over the diagrams in the download section.

I have several 2 carb manifolds and considered using them with the Deluxe style oil bath air cleaners modified to use dry filters. That would allow the use of the side filter described above. They may be more efficient that way but they will be louder. I am hoping the 57 filter ( which has the silencing chamber ) will be silent.

 

[Bob Riding]

Me too! I recently rebuilt the WW Stromberg and after our discussions, I'm really looking forward to experiencing the difference between it and the old Carter 1bbl.

 

My air cleaner is from a '56 Suburban. I actually have two -one has a small pipe brazed into the lid...would it be big enough for a PCV setup?

[Loren]

In your photo ( at the top ) of the manifold, just under the choke inlet there's a boss. On my 49 ( single barrel ) manifold. that boss is drilled and tapped ( plugged however ) for the vacuum connection to the PCV. I don't know why they didn't drill and tap the later manifold but that is where it goes.

I have the same manifold and it is not drilled either.

Upon further inspection of my parts I found that somebody had milled the intake manifold at the ports by about an 1/8th of an inch!

If I milled that much off the exhaust manifold it would not be good. The web between the adjacent ports would disappear.

So I am going to spray weld the intake to build it back up.

Since I am doing that I will skin the exhaust at the ports and the heat riser area, then spray weld them as well.

Once the welding is done I can bolt them together and machine the port surface at the same time.

 

Here's the photo of the "Emission Control Filter" from NAPA.

This one is the most common GM type. It's hell getting old! they used to have them on a rack where you could pick through them. Now since carburetors are for antiques they put them in back on the shelves and you have to know what you want because the counter kids weren't born yet!

[JBNeal]

additional information - NOS oil filler caps

In one of my parts hauls, I encountered a smashed Mopar oil filler cap...the filter element looked like a brillo pad.

[Bob Riding]

On 3/7/2023 at 11:28 AM, Loren said:

In your photo ( at the top ) of the manifold, just under the choke inlet there's a boss. On my 49 ( single barrel ) manifold. that boss is drilled and tapped ( plugged however ) for the vacuum connection to the PCV. I don't know why they didn't drill and tap the later manifold but that is where it goes.

I have the same manifold and it is not drilled either.

Upon further inspection of my parts I found that somebody had milled the intake manifold at the ports by about an 1/8th of an inch!

If I milled that much off the exhaust manifold it would not be good. The web between the adjacent ports would disappear.

So I am going to spray weld the intake to build it back up.

Since I am doing that I will skin the exhaust at the ports and the heat riser area, then spray weld them as well.

Once the welding is done I can bolt them together and machine the port surface at the same time.

 

Here's the photo of the "Emission Control Filter" from NAPA.

This one is the most common GM type. It's hell getting old! they used to have them on a rack where you could pick through them. Now since carburetors are for antiques they put them in back on the shelves and you have to know what you want because the counter kids weren't born yet!

Thanks for making a special trip to the parts store! Now I can understand what you were describing. Do you suggest I drill and tap my boss like your '49, or use the existing plugged outlet on the left runner? Also, are you following the VPW style setup or the one that @MarcDeSotoposted or you own design?

[Eneto-55]

I don't think I would consider soaking with gasoline (or some other flammable) and setting it on fire - I seem to recall that the manual says that the fibers in the oil bath are horse hair.  You would end up with an empty one, like I did when I soaked mine in the degreaser solution at the plating shop.  (This tank was steam heated to just below boiling, and it must have dissolved the horse hair.  I wish I could still remember the name of the powered stuff we used in that soak tank, but it was too long ago - like over 40 years back.)  I opened the crimp around the top of the upper canister of the oil bath, and so just need to find a suitable material to replace the horse hair with.  (I guess I could trim some horses' tails up at the grocery store....  Just kidding.  The Amish owners wouldn't be happy about that.)

[Loren]

Here's my take on a PCV setup.

I used all common GM parts simply because they are available CHEAP.

In these photos you will see the Road Draft Tube from my 49 P17. Not all Plymouths have the same parts. I have seen a single piece tube with a bolt holding it in place. This one has a filter and is in two pieces. What I like about is you can "put it back to stock" really quickly ( if that matters ).

On mine the outlet pipe was spot welded in 4 places and there was a gap around it. I brazed the outlet pipe in to seal it.

The GM grommet just pushes in and the rolled edge of the road draft tube holds in. When you push in the PCV valve it is locked in place very well.

There is a groove inside the grommet that would lock the PCV valve in place but I suspect you'd never get it apart again once in the Road Draft Tube.

NAPA P/N 630-1038 Grommet P/N 2-9220 PCV valve.

 

The manifold photo shows the plug I spoke of earlier.

The plug on the top surface of the runner to cylinders 5 & 6 is the vacuum connection for the wipers. Ideally you'd want to use the bigger connection for the PCV. There are alternatives of course. If you don't want to be boring holes in your nice manifold you can get a vacuum connection plate on eBay for a South Wind heater. They are made for just about every kind of one and two barrel carburetor. I have seen ones for your Stromberg WW for around $8.

[JBNeal]

21 hours ago, Eneto-55 said:

I don't think I would consider soaking with gasoline (or some other flammable) and setting it on fire - I seem to recall that the manual says that the fibers in the oil bath are horse hair.  ...

the oil bath air filters, now thems have a cellulose horse hair filter element...but the crankcase vented fill cap, they have interwoven metal strands as a filter element...soak in diesel for a days, drain, ignite...clean as a whistle by the time the smoke clears, but the outside might need slicking up afterwards with some Rustoleum black 

[andyd]

Any of those "horse hair" or wire fibre type filters whether in an aircleaner or oil filler cap I just soak in a heavy duty degreaser or in an aircleaner wipe out then soak for an hour or so then just wash them out with a strong hose jet, then leave the mesh to dry for a few hours or overnight........its just oil & crap, degreased & its clean again............andyd

[Bob Riding]

On 3/10/2023 at 2:32 PM, Loren said:

Here's my take on a PCV setup.

I used all common GM parts simply because they are available CHEAP.

In these photos you will see the Road Draft Tube from my 49 P17. Not all Plymouths have the same parts. I have seen a single piece tube with a bolt holding it in place. This one has a filter and is in two pieces. What I like about is you can "put it back to stock" really quickly ( if that matters ).

On mine the outlet pipe was spot welded in 4 places and there was a gap around it. I brazed the outlet pipe in to seal it.

The GM grommet just pushes in and the rolled edge of the road draft tube holds in. When you push in the PCV valve it is locked in place very well.

There is a groove inside the grommet that would lock the PCV valve in place but I suspect you'd never get it apart again once in the Road Draft Tube.

NAPA P/N 630-1038 Grommet P/N 2-9220 PCV valve.

 

The manifold photo shows the plug I spoke of earlier.

The plug on the top surface of the runner to cylinders 5 & 6 is the vacuum connection for the wipers. Ideally you'd want to use the bigger connection for the PCV. There are alternatives of course. If you don't want to be boring holes in your nice manifold you can get a vacuum connection plate on eBay for a South Wind heater. They are made for just about every kind of one and two barrel carburetor. I have seen ones for your Stromberg WW for around $8.

Thanks!! I ordered the parts- very inexpensive. Is this the vacuum plate you were referring to for the WW Stromberg?

NOS Stewart Warner South Wind Heater No. 46 Vacuum Kit OEM Chevrolet Ford Dodge

I like the idea of NOT drilling into my manifold!